1. Field of the Invention
The invention relates to a fiber-optic conversion module as part of a lighting device on a vehicle, in particular as part of a headlight.
2. Description of Related Art
A light emitting device as part of a headlight is known from WO2008000208A1 (DE 10 2006 029 203 A1) and comprises an excitation light source and coupled thereto an optical fiber and downstream thereof a converter material for converting the excitation light of shorter wavelengths into useful light of an on average longer wavelength having an appearance of white light. The useful light, in this case, is composed of a longer wavelength fraction of converted light and an unconverted fraction of the excitation light. In detail, a plug-in connection to a transparent body, a converter in transmission mode, and an optical component for emitting the converted useful light in a preferred direction are provided. A cooling element for the converter is not provided. When in such a light emitting device an optical fiber becomes damaged, this may lead to dangerous situations in case lasers are used as the excitation light sources. Therefore, the light emitting device is provided with additional detection means for detecting damage to the one or more optical fibers and, if necessary, to shut off the power supply to the excitation light source. The detection means may be provided on the light input end for excitation light to receive light fed back from the converter, which indicates that the optical fiber is operational and intact. Another method of failure detection is to check for current flow in a network of wires including one or more wires running through the cladding regions of the one or more optical fiber(s). When an optical fiber breaks, the co-extending wire should also break, which would cause an interruption of current flow and lead to failure detection. In the event of a failure, the radiation source is shut off. The light emitting device has a configuration such that the conversion material only works in transmission. Cooling of the converter material is very difficult to accomplish in this case. However, effective cooling is indispensable because of the heat produced during conversion.
From DE 10 2010 034 054 A1 a laser-based white light source is known, in which a laser produces a light spot in a converter by means of a converging lens, for delivering white useful light in a transmission mode. In order to avoid high temperatures at the light spot, the converter is produced using thermally conductive material and is additionally cooled by air and/or is rotated to cause the light spot to move around in the converter material.
The use of a plurality of optical fibers adjacent to each other in a light emitting device that includes a converter in transmission mode is known from US 2010/0254153 A1.
US 2008/0075406 A1 discloses an optical component comprising a converter, an optical fiber leading thereto, a holding member for the optical fiber, and a cap for securing the converter to the holding member. The cap and the holding member are made of a material of high thermal conductivity for preferably removing heat from the converter which is operated in transmission.
Light emitting devices for headlights, in part also in remission mode, are known from US 2011/0148280 A1, US 2011/0279007 A1, US 2011/0280033 A1, US 2012/0106178 A1, US 2012/0106183 A1, and US 2012/0069593 A1. Here, the converter material is arranged in form of a block in the focus of the parabolic headlight mirror, with a transparent plate extending transversely through the parabolic mirror for fixing the converter (US 2011/0148280 A1, US 2011/0279007 A1, US 2011/0280033 A1, US 2012/0069593 A1), or a support wall is formed along the axis of the parabolic mirror, to which the converter is mounted (US 2012/0106178 A1, US 2012/0106183 A1). A fiber-optic conversion module provided with connectors for injecting light at one end and with a light exit window for emitting useful light at the other end and mountable as a whole in a working unit, for example a parabolic mirror, is not specified in the cited documents.